Light guide illumination device with light divergence modifier

Abstract

An illumination device includes a light-emitting element (LEEs); a light guide extending in a forward direction from a first end to a second end to receive at the first end LEE light and to guide the light to the second end, such that divergence of the light received at the first end and divergence of the guided light that reaches the second end are substantially the same; a light divergence modifier optically coupled to the light guide at the second end to receive the guided light, to modify the divergence of the guided light, such that the light provided by the light divergence modifier has a modified divergence different from the divergence of the guided light; and an optical extractor optically coupled to the light divergence modifier, to output into the ambient environment light provided by the light divergence modifier as output light in one or more output angular ranges.

What is claimed is: 
     
       1. An illumination device comprising:
 a plurality of light-emitting elements (LEEs) to emit light having a first divergence; 
 one or more optical couplers to redirect emitted light, each optical coupler having a receiving aperture optically coupled with a corresponding one or more LEEs to receive the emitted light, and further having an opposing aperture, the optical coupler being flared such that the receiving aperture is smaller than the opposing aperture, thereby light provided by the optical coupler at the opposing aperture has a second divergence smaller than the first divergence; 
 a light guide comprising a pair of opposing side surfaces that are parallel to each other and extend in a forward direction from a first end of the light guide to a second end of the light guide, the light guide being positioned to receive at the first end light provided by the one or more optical couplers and configured to guide the light to the second end, wherein guided light that reaches the second end has a third divergence that is substantially the same as the second divergence, wherein a numerical aperture of the light guide is such that the light received from the one or more optical couplers with the second divergence can be guided by the light guide through TIR off the pair of opposing side surfaces; 
 a light divergence modifier having an input aperture optically coupled to the light guide at the second end to receive the guided light and further having an output aperture, the light divergence modifier being flared such that the input aperture is smaller than the output aperture, thereby light provided by the light divergence modifier at the output aperture has a modified divergence smaller than the third divergence of the guided light; and 
 an optical extractor optically coupled to the output aperture of the light divergence modifier and comprising a first redirecting surface, the first redirecting surface of the optical extractor being adapted to reflect at least a portion of the light provided by the light divergence modifier in a first direction that has a component orthogonal to the forward direction and another component in a backward direction, such that the optical extractor outputs into the ambient environment light reflected by the first redirecting surface as first output light in a first output angular range, wherein the first output angular range relates to the first direction. 
 
     
     
       2. The illumination device of  claim 1 , wherein the light divergence modifier comprises a pair of opposing side surfaces extending along a length of the light divergence modifier between the input aperture and the output aperture. 
     
     
       3. The illumination device of  claim 2 , wherein at least one of the opposing side surfaces is planar. 
     
     
       4. The illumination device of  claim 3 , wherein both of the opposing side surfaces are planar. 
     
     
       5. The illumination device of  claim 2 , wherein the length of the light divergence modifier is a fraction of a length of the light guide. 
     
     
       6. The illumination device of  claim 5 , wherein the fraction is between 5% and 50%. 
     
     
       7. The illumination device of  claim 2 , wherein the light guide, the light divergence modifier and the optical extractor are integrally formed or bonded together. 
     
     
       8. The illumination device of  claim 1 , wherein the light divergence modifier comprises a truncated conical shaped surface extending between the input aperture and the output aperture. 
     
     
       9. The illumination device of  claim 1 , wherein the light divergence modifier is configured to guide the light received at the input aperture in the forward direction through total internal reflection (TIR) at the opposing side surfaces. 
     
     
       10. The illumination device of  claim 1 , wherein the LEEs are LEDs that emit white light. 
     
     
       11. The illumination device of  claim 1 , wherein the optical extractor comprises a second redirecting surface adapted to reflect at least a portion of the light provided by the light divergence modifier in a second direction that has a component antiparallel to the orthogonal component of the first direction and another component in the backward direction, such that the optical extractor outputs into the ambient environment light reflected by the second redirecting surface as second output light in a second output angular range, wherein the second output angular range relates to the second direction. 
     
     
       12. The illumination device of  claim 11 , wherein the first redirecting surface and/or the second redirecting surface transmits a remaining portion of the light provided by the light divergence modifier so that the transmitted portion of the light exits the optical extractor to the ambient environment in the forward direction. 
     
     
       13. The illumination device of  claim 11 , wherein
 the optical extractor comprises a first curved output surface and a second curved output surface positioned in respective paths of the light reflected from the first redirecting surface and the second redirecting surface, and 
 the first curved output surface and the second curved output surface are configured to transmit light incident thereon to the ambient environment in respective backward angular ranges. 
 
     
     
       14. The illumination device of  claim 1  extends orthogonally to the forward direction. 
     
     
       15. The illumination device of  claim 14 , wherein the LEEs are arranged orthogonally to the forward direction.